Semiconductor device manufacturers are constantly striving to shrink or scale device sizes. However, as scaling continues, quantum mechanical constraints will limit the minimum feature sizes of the semiconductor devices. Thus, semiconductor device manufacturers are seeking methods of exploiting the physical properties of the semiconductor material, i.e., manufacturing devices in accordance with their quantum mechanical properties. One such device type is a quantum multi-function device. These types of devices utilize quantum mechanical effects such as interband resonant tunneling and electrons confined in quantum box structures.
Since the superior electrical performance of these types of devices is largely due to their exploitation of quantum effects produced by the appropriate stacking together of a series of ultra-thin semiconductor layers with thicknesses of the order of tens of angstroms or less each, they are particularly sensitive to the presence of contaminants that arise during the various processing steps. For example, the accumulation of a mono-atomic layer of carbon at the interface between two of the ultra-thin layers may adversely affect the performance of the device. Device processing steps such as patterning and etching carried out in a conventional manner may introduce a sufficient number of contaminants to render these devices inoperative. Further, some process steps, e.g., patterning and etching are performed at one location within a fabrication facility, whereas other process steps, e.g., epitaxial growth, are performed at a different location within the fabrication facility. Typically the semiconductor substrates are exposed to air during their transport from one processing location to another. During the transport step, they are susceptible to contamination by particulates in the air.
Accordingly, it would be advantageous to have a method of fabricating quantum multi-function devices that eliminates contamination by air. It would be further advantageous for the method to include epitaxial re-growth steps that minimize the number of process steps that contaminate the devices.